<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .case2 {
            min-height: 200px;
            height: auto;
            background: red;
            margin-bottom: 20px;
        }

        .case2-inner {
            height: 0;
            margin-bottom: 50px;
        }
    </style>
</head>

<body>
    <div class="case2">
        <div class="case2-inner"></div>
    </div>
    <div>为了看间距效果</div>
</body>

</html>